This invention relates to an in-line color picture tube apparatus with a dynamic convergence correction device suitable for use, for example, in an apparatus which necessitates reproduction of high resolution pictures.
Heretofore, in in-line color picture tubes, it has been general practice to use, for the correction of static convergence, a four-pole ring magnet and a six-pole ring magnet which are mounted on the outer periphery of the neck portion of the tube. When the static convergence correction is effected by moving such two ring magnets, however, the mechanical operation thus involved renders the work of correction very difficult. There consequently ensues a problem that the work calls for skill. To solve this problem, there has been proposed a device which has eight coils disposed at a spacing of 45.degree. circumferentially of the outer periphery of the neck portion of the tube and feeds a direct electric current to the coils so as to generate a four-pole magnetic field having a horizontal axis (in the direction of the alignment of in-line electron guns), a four-pole magnetic field having an axis making an angle of 45.degree. with respect to the horizontal axis, a six-pole magnetic field having the horizontal axis, and a six-pole magnetic field having a vertical axis and effect mutual correction of the outer beams of the in-line three electron beams in the horizontal and vertical directions and mutual correction of the outer beams and the central beam in the horizontal and vertical directions, thereby accomplishing the correction of static convergence (Japanese Patent Preliminary Publication No. 71723/76).
With the static convergence correction device of this type, although the correction of static convergence may be smoothly effected, it is difficult even by use of a self-convergence deflection yoke to effect highly accurate correction of convergence which covers the peripheral regions of the picture screen in high resolution color picture tubes. Particularly when the high resolution color picture tube is used as a terminal display unit for a computer, it is required to clearly display Chinese characters and the like characters at regions of the picture screen ranging from center to periphery. The conventional device was difficult to achieve the clear display all over the screen.
To cope with the difficulty, it becomes necessary to use means capable of correcting the residual misconvergence which escapes the correction by the self-convergence deflection yoke. To date, there has never been developed dynamic convergence correction means which has high sensitivity and yet refrains from causing any disturbance in the magnetic field of the self-convergence deflection yoke.
As well known in the art, it is essential to provide a dynamic convergence correction device in delta type electron gun color picture tube for the sake of assuring the operation of the tube. However, an in-line color picture tube apparatus with a dynamic convergence device capable of correcting a residual misconvergence that cannot be corrected by the self-convergence deflection yoke has not yet been available.